[Solr Wiki] Update of "WritingDistributedSearchComponents" by GrantIngersoll

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The "WritingDistributedSearchComponents" page has been changed by GrantIngersoll.
http://wiki.apache.org/solr/WritingDistributedSearchComponents?action=diff&rev1=6&rev2=7

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  = Basics =
+ 
+ /!\ Note: Best efforts are being made to make this reliable, but please consider it a work in progress. /!\ 
  
  A Distributed !SearchComponent is a !SearchComponent that overrides one or more of the following methods:
   1. [[http://lucene.apache.org/solr/api/org/apache/solr/handler/component/SearchComponent.html#distributedProcess(org.apache.solr.handler.component.ResponseBuilder)|distributedProcess]]
@@ -19, +21 @@

  The basic distributed algorithm (which is a different path from the non-distributed), as implemented in [[http://lucene.apache.org/solr/api/org/apache/solr/handler/component/SearchHandler|SearchHandler]] is:
   1. while not at STAGE_DONE
       1. For each Component invoke distributedProcess to see if it has anything it wants to distribute.  If it does, it will return one of the 4 stages and setup a !ShardRequest and add it to a queue
+           1. modifyRequest() can be used to refine other shard requests, instead of sending a separate !ShardRequest.  See the [[http://lucene.apache.org/solr/api/org/apache/solr/handler/component/FacetComponent|FacetComponent]] for an example.  This is likely best done by calling ResponseBuilder.addRequest() which will then invoke the modifyRequest() method on each of the components.
+           1. Components can also indicate the purpose of their request by using the ShardRequest.PURPOSE_* fields.  When set, these fields can then be inspected by the other components to see if it is a purpose they are interested in.
       1. While we have outgoing !ShardRequest instances
            1. Submit the requests to the shards
            1. For each component, handle the responses
       1. For each component, call finishStage() 
  In this process, each !ShardRequest then goes off to it's Shard just as if it were a normal request of that server.
  
- For those wondering, modifyRequest() can be used to refine other shard requests, instead of sending a separate !ShardRequest.  See the [[http://lucene.apache.org/solr/api/org/apache/solr/handler/component/FacetComponent|FacetComponent]] for an example.  /!\ :TODO: /!\ CONFIRM THIS.
+ 
  
  = Testing =